Refrigerant charging method and apparatus

ABSTRACT

A refrigerant charge adjusting device, especially useful in air conditioning systems with capillary tube expansion device, comprises a target into which liquid refrigerant from the suction line is bled after the system has been slightly overcharged. The liquid refrigerant striking the target will cause a layer of frost to form on the target providing a visual indication that liquid refrigerant is passing through the suction gas line (also indicating zero superheat). The refrigerant is continuously bled through the orifice impinging on the target until such time as the refrigerant becomes superheated and will melt the front on the target. The system is bled for a predetermined time period after all frost has disappeared to insure satisfactory refrigerant charge. The length of the predetermined time depends on the rate of bleed permitted through the orifice. The invention further contemplates an improved charge adjusting tool tube used in carrying out the foregoing method.

United States Patent 11 1 Maudlin 1 1 REFRIGERANT CHARGING METHOD AND APPARATUS Wendell E. Maudlin, York, Pa.

[73] Assignee: Borg-Warner Corporation, Chicago,

Ill.

[75] Inventor:

[22 Filed: Dec. 28, 1973 211 App1.No.:429,429

s21 u.s.c1. ..62/77;62/128;62/129; 62/292 [51] 1m.c1. ,.F25b 45/00 [58] Field of Search 62/77, 125, 149, 128, 129, 62/292; 165/174, 111

Primary Examiner--Meyer Perlin Attorney, Agent, or FirmThom-as B. Hunter 1451 May 20, 1975 [57] ABSTRACT A refrigerant charge adjusting device, especially useful in air conditioning systems with capillary tube expansion device, comprises a target into which liquid refrigerant from the suction line is bled after the system has been slightly overcharged. The liquid refrigerant striking the target will cause a layer of frost to form on the target providing a visual indication that liquid refrigerant is passing through the suction gas line (also indicating zero superheat). The refrigerant is continuously bled through the orifice impinging on the target until such time as the refrigerant becomes superheated and will melt the front on the target. The system is bled for a predetermined time period after all frost has disappeared to insure satisfactory refrigerant charge. The length of the predetermined time depends on the rate of bleed permitted through the orifice. The invention further contemplates an improved charge adjusting tool tube used in carrying out the foregoing method.

2 Claims, 3 Drawing Figures REFRIGERANT CHARGING METHOD AND APPARATUS BACKGROUND AND SUMMARY OF THE INVENTION This invention relates primarily to a method and apparatus for correctly charging refrigerant into a refrigeration system. In the past, various techniques have been used to correctly determine whether a system has been properly charged. Some of these techniques require the use of test gauges operated by a relatively highly skilled technician. Others require a considerable amount of calculation and guesswork which often results in improper charging of the system. For example, as described in US. Pat. No. 2,689,463 a complex system of valves, sensorsand gauges is used to determine the correct charge to a system. A more simplified technique is described in US. Pat. No. 3,237,420 in which a bleeder tool is adapted to time the amount of bleed required to bring the refrigerant charge down to the designed charge; but this requires that the serviceman know in advance exactly how much refrigerant to remove.

In the present invention, the method and apparatus are described in which the charging is extremely simple, requires no complicated gauges or valves, has no moving parts, and reduces the charging time to a very few minutes.

The charge adjusting tool is designed especially for use in airconditioning systems using capillary tube expansion devices. The principle of operation starts with an overcharged system and uses a controlled bleed-off of refrigerant until the proper charge level is achieved.

Satisfactory charging can be achieved with the system in operation, with comfort conditions existing inside the house and ambient outdoor temperatures from 75 to 100F. The principle of operation further requires a bleed target which is connected to the suction gas line and on which refrigerant impinges after it is bled to atmosphere. When the system is overcharged, liquid refrigerant will be delivered through the orifice causing a layer of frost to form on the target which can be determined by visual inspection. Eventually, the suction gas will become superheated and the frost on the target will melt. To assure an accurate charge, additional refrigerant is bled after the frost has melted for a predetermined time, depending on the rate of bleed built into the system.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a detailed cross-sectional view of a refrigerant charge adjusting device forming the subject of the present invention;

FIG. 2 is a cross-sectional view taken along the plane .of line 22 of FIG. 1; and

FIG. 3 is a schematic or diagrammatic representation of a conventional refrigeration circuit.

DETAILED DESCRIPTION OF THE INVENTION Referring first to FIG. 3, there is shown a typical refrigeration circuit including a compressor 10, a condenser 12, a capillary or other fixed restrictor expansion device 14, and an evaporator 16. The suction gas line 18, which connects evaporator 16 with compressor 10, is provided with a fitting 20 to which the charge adjusting device may be connected. In the present invention, a simple Schraeder valve, of the type used in pneumatic tires, may be installed in the line. Similarly, means may be provided for introducing refrigeration into the system through valve 20.

The charge adjusting device, shown in FIGS. 1 and 2, is generally designated by reference numeral 21. The charging device comprises an elongated tubular member 22 having a closed end 22 and an open end 22b to which a threaded connector 24 is connected for attachment to the Schraeder type valve. Inside the fitting is agasket 26 to provide sealing contact with the valve. When the device is connected to the fitting 20 in suction line 18 a valve depressor 28 of the Schraeder type is located in the center and makes contact with the valve element (not shown) to permit the flow of refrigerant into the tube.

Tubular member 22 is further provided with a sleeve element 30, preferably of metal or other material with good heat transfer properties, which has one end 30a in sealing contact with the outside surface of tubular member 22 and has an opening 32 at the opposite end. The sleeve element 30 provides an elongated annular space 34 between the outside surface of tubular member 22 and the inside surface of sleeve 30. The opening 32 at the end provides a passage 36 for refrigerant to flow to atmosphere. Refrigerant metering ports or port 38 are provided in the tubular member so that the liquid refrigerant flows into the annular space 34 and forms a pool in contact with a substantial portion of the sleeve member 30, regardless of the position of the charge testing device. This insures that the frost which will form on the outside of sleeve member 30 will be over a substantial area thereof to facilitate visual inspection. The refrigerant of course will boil and the resulting vapor will flow through passage 36 to atmosphere. i

OPERATION The system is first overcharged by addingrefrigerant thereto in the conventional manner. An overcharge is indicated by a cool compressor, condensed moisture (sweat) accumulation on the compressor and a suction line that is excessively cold to the touch.

The charging device 2lis then installed by threading the connector portion 24 onto the Schraeder valve fitting 20. The valve depressor 28 will contact the 'pin (not shown) in valve to start flow into the device. The outside surface of sleeve element 30 will immediately turn white with frost as the refrigerant boils in the annular space 34. The vapor will flow to atmosphere through passage 36. The frost will remain as long as any liquid refrigerant is in the suction line..If frost does not appear, the system was not overcharged; so that more refrigerant must be added and the sequence repeated.

When the suction gas becomes superheated, the frost will melt. The device is left installed until about 2 minutes after all frost has melted. The device may then be removed and the system rescaled. The exact time period may vary depending on the bleed characteristics of the device. Such devices are calibrated to insure 5-l0F superheat after the predetermined time period has expired.

While this invention has been described in connection with a specific embodiment thereof, it is to be understood that this is by way of illustration and not by way of limitation; and the scope of the appended claims should be construed as broadly as the prior art will permit.

What is claimed is:

l. A method of charging a refrigeration system of the type including a compressor, a condenser, a fixed restriction expansion device and an evaporator all connected to provide a closed circuit, vapor cycle refrigeration system and including a suction gas line between said evaporator and said compressor comprising the steps of: initially charging said refrigeration system by adding refrigerant thereto until a slightly overcharged condition exists; providing a target into which bleed-off liquid refrigerant may be conducted from said suction gas line to said target, thereby indicating the overcharged condition; continuing to bleed-off liquid refrigerant until the frost on said target is completely melted, thereby indicating a superheated condition of suction gas; discontinuing the bleed-offof refrigerant when a predetermined time has elapsed after all frost has been melted, said predetermined time being sufficient to insure 5l0F of superheat.

2. A refrigerant charge adjusting device comprising: an elongated tubular member having a first closed end portion and a second end portion having a threaded section and a sealing gasket adapted to be connected to a suction gas line in a refrigeration system; a sleeve member surrounding said tubular member and forming an annular space extending along a portion of the length of said tubular member, said sleeve having one end thereof in sealing contact with said tubular member and having an opening at the other end thereof through which said tubular member extends and providing a path for gas flow between said sleeve member and said tubular member, said sleeve member being formed of material having good thermal conducting properties; and means defining a refrigerant metering port'in said tubular member communicating with said annular space. 

1. A method of charging a refrigeration system of the type including a compressor, a condenser, a fixed restriction expansion device and an evaporator all connected to provide a closed circuit, vapor cycle refrigeration system and including a suction gas line between said evaporator and said compressor comprising the steps of: initially charging said refrigeration system by adding refrigerant thereto until a slightly overcharged condition exists; providing a target into which bleed-off liquid refrigerant may be conducted from said suction gas line to said target, thereby indicating the overcharged condition; continuing to bleed-off liquid refrigerant until the frost on said target is completely melted, thereby indicating a superheated condition of suction gas; discontinuing the bleed-off of refrigerant when a predetermined time has elapsed after all frost has been melted, said predetermined time being sufficient to insure 5*-10*F of superheat.
 2. A refrigerant charge adjusting device comprising: an elongated tubular member having a first closed end portion and a second end portion having a threaded section and a sealing gasket adapted to be connected to a suction gas line in a refrigeration system; a sleeve member surrounding said tubular member and forming an annular space extending along a portion of the length of said tubular member, said sleeve having one end thereof in sealing contact with said tubular member and having an opening at the other end thereof through which said tubular member extends and providing a path for gas flow between said sleeve member and said tubular member, said sleeve member being formed of material having good thermal conducting properties; and means defining a refrigerant metering port in said tubular member communicating with said annular space. 